Automotive ignition systems generally employ a power switching circuit that alternately makes and breaks an electrical connection from the battery, through an ignition coil to ground. The switching is typically based on a signal received from an engine control unit which is timed to fire the engine spark plugs as needed for operation of the engine. The switching circuit, which may be implemented as an integrated circuit (IC), requires a supply voltage to power the circuit and its constituent components. This supply voltage is generally provided by the vehicle battery and may therefore include high voltage transients, large voltage swings, high frequency noise and other artifacts that can be detrimental to the switching circuit.
Additional circuitry is therefore needed to protect the switching circuit IC from these voltage transients as well as from electrostatic discharge (ESD). The protection circuitry, which may include larger resistors and capacitors, can consume up to half of the IC area, or more, in some cases. This typically results in increased size and cost for the switching circuit IC and may adversely impact reliability if these harsh environmental conditions imposed by the battery are not adequately filtered by the protection circuitry.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.